The above-mentioned compound [XVI] useful as an HIV protease inhibitor is known as described in WO95/09843. This compound [XVI] has been conventionally produced from serine as a starting material, by increasing carbon and numerous other steps inclusive of stereoselective reduction of carbonyl group. Such conventional production method is extremely complicated and inefficient, since it requires expensive starting materials and constant low temperature conditions for reactions. Accordingly, there remain many problems to be solved before the conventional synthetic method is actually put to industrial practice.
In addition, 2,2-dimethyl-6-amino-1,3-dioxepan-5-ol which is described, for example, in U.S. Pat. No. 4,439,613 is an intermediate for producing a compound useful as an X ray contrast medium, and even though the compound obtained is a racemate, resolution of the racemate itself by a method such as recrystallization has been extremely difficult. Moreover, this U.S. patent does not suggest production of specific enantiomers of the present invention.
Accordingly, an object of the present invention is to provide a method for stereoselectively and extremely efficiently producing the above-mentioned compound [XVI] useful as an HIV protease inhibitor upon solution of the above-mentioned problems. Another object of the present invention is to provide a novel intermediate useful for producing said compound and a production method thereof.